How can I make the waveform in sequencer bigger?
From official manual:

https://docs.blender.org/manual/en/2.80/editors/vse/sequencer/navigating.html


  Use these shortcuts to adjust the sequence area of the VSE:
  
  
  Scale View, Ctrl-MMB and drag up/down (vertical scale) or left/right    (horizontal scale).
  Scale View Vertically, drag on the circles on the vertical scroll bar.
  Scale View Horizontally, drag on the circles on the horizontal scroll bar.